1 files changed, 45 insertions, 0 deletions
diff --git a/source/blender/compositor/operations/COM_BrightnessOperation.cc b/source/blender/compositor/operations/COM_BrightnessOperation.cc
index 92cab47318a..7878eca2bbd 100644
--- a/source/blender/compositor/operations/COM_BrightnessOperation.cc
+++ b/source/blender/compositor/operations/COM_BrightnessOperation.cc
@@ -28,6 +28,7 @@ BrightnessOperation::BrightnessOperation()
   this->addOutputSocket(DataType::Color);
   this->m_inputProgram = nullptr;
   this->m_use_premultiply = false;
+  flags.can_be_constant = true;
 }
 
 void BrightnessOperation::setUsePremultiply(bool use_premultiply)
@@ -85,6 +86,50 @@ void BrightnessOperation::executePixelSampled(float output[4],
   }
 }
 
+void BrightnessOperation::update_memory_buffer_partial(MemoryBuffer *output,
+                                                       const rcti &area,
+                                                       Span<MemoryBuffer *> inputs)
+{
+  float tmp_color[4];
+  for (BuffersIterator<float> it = output->iterate_with(inputs, area); !it.is_end(); ++it) {
+    const float *in_color = it.in(0);
+    const float brightness = *it.in(1) / 100.0f;
+    const float contrast = *it.in(2);
+    float delta = contrast / 200.0f;
+    /*
+     * The algorithm is by Werner D. Streidt
+     * (http://visca.com/ffactory/archives/5-99/msg00021.html)
+     * Extracted of OpenCV demhist.c
+     */
+    float a, b;
+    if (contrast > 0) {
+      a = 1.0f - delta * 2.0f;
+      a = 1.0f / max_ff(a, FLT_EPSILON);
+      b = a * (brightness - delta);
+    }
+    else {
+      delta *= -1;
+      a = max_ff(1.0f - delta * 2.0f, 0.0f);
+      b = a * brightness + delta;
+    }
+    const float *color;
+    if (this->m_use_premultiply) {
+      premul_to_straight_v4_v4(tmp_color, in_color);
+      color = tmp_color;
+    }
+    else {
+      color = in_color;
+    }
+    it.out[0] = a * color[0] + b;
+    it.out[1] = a * color[1] + b;
+    it.out[2] = a * color[2] + b;
+    it.out[3] = color[3];
+    if (this->m_use_premultiply) {
+      straight_to_premul_v4(it.out);
+    }
+  }
+}
+
 void BrightnessOperation::deinitExecution()
 {
   this->m_inputProgram = nullptr;